The deglaciation and early postglacial environmental history of southcentral Newfoundland: evidence from the palynostratigraphy and geochemical stratigraphy of lake sediments

Vardy, Sheila R. (1991) The deglaciation and early postglacial environmental history of southcentral Newfoundland: evidence from the palynostratigraphy and geochemical stratigraphy of lake sediments. Masters thesis, Memorial University of Newfoundland.

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Abstract

The purpose of this thesis is to reconstruct the chronology of deglaciation and early Holocene environmental change in southcentral Newfoundland. Previous palynological studies have helped to define the timing of deglaciation and the sequence of postglacial environmental change in certain parts of Newfoundland, but a firm chronology of events for the entire island has not yet been established. -- Radiocarbon dating, pollen analysis and geochemical analysis have been carried out on sediment cores from four ponds, including three within the proposed limit of the main Newfoundland ice cap and one from the Hermitage Peninsula, which was apparently affected by a smaller local ice cap. The pollen, sediment and geochemical stratigraphies of the basal sediments of these cores confirm that the basal radiocarbon dates represent early stages in the postglacial sequences. The basal dates from Northwest Gander River Pond (10,200 ± 240 BP; GSC-5027), Moose Pond (10,000 ± 170 BP; GSC-5029) and Pool's Cove (9710 ± 120 BP; GSC-4945) are therefore considered minimum ages of deglaciation, but it is difficult to determine when the Conne River site became ice free since the basal date of 11,300 ± 100 BP (GSC-3436; Blake, 1983) is suspected of being too old. -- All four sites were apparently ice covered during the Late Wisconsinan, and there is no evidence that deglaciation occurred before the Younger Dryas episode. It is inferred that all three sites within the limit of the main Newfoundland ice cap were ice free before 10,000 BP, and that deglaciation progressed by downwasting, possibly beginning by 10,500 BP in areas of high elevation. The basal date of 9710 ± 120 BP (GSC-4945) from Pool's Cove Pond on the Hermitage Peninsula provides a minimum date of deglaciation, but this site may have been ice free by 10,100 BP. -- The reconstruction implies that deglaciation of southcentral Newfoundland began in the middle of the Younger Dryas cold period, and can therefore only be considered tentative, especially in light of doubts about the accuracy of bulk sediment radiocarbon dating of basal lake sediments.

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